Assistive walking device

About the solution

Jon Christiansen was a sea captain. In 1985 he was hired to sail a replica of the Godspeed.

One day while he was cleaning the ship's hull, someone spun the wheel, trapping Christiansen's leg between the rudder and a support post. The accident severed or damaged most of the nerves below his left knee. Doctors told him he would never have feeling in his left foot again.

Christiansen had the strength to walk with a cane, but without feeling in his foot, he could not know when each step hit the ground without looking down. After a painful fall in 2003, he recruited two friends, engineers Richard Haselhurst and Steve Willens, to help him find a better way to get around. Willens came up with the idea of using tones to signal Christiansen's brain when his foot touched the ground, and in 2006 the three built a prototype of Sensastep.

"I was stepping off a gangway, and just went straight down," Christiansen explains. "So my wife said, 'We've gotta come up with something that tells you where your foot is.' "

To use Sensastep, the patient wears a conductive foam insole embedded with 13 pressure sensors. As the heel or toe strikes the ground, a transmitter strapped to the ankle sends signals to a receiver that's slipped over the ear. The earpiece vibrates against the bone behind the ear, stimulating the cochlear nerve. Variations in the vibrations, which the patient perceives as audible tones, alert the brain to which part of the foot has contacted the ground. Christiansen and other patients will not need to look down and watch every step they take to avoid falls anymore.

Sensastep could help patients with sensory and motor-skill disabilities caused by diabetic neuropathy or Parkinson's disease, as well as those with balance problems from strokes or injuries. Compared with other assisted walking devices, it will be convenient: the insole fits in any shoe, and the ankle and earpiece charge like a cellphone. The inventors have also developed an app to track patients' improvement.

"It's basically like a jumper cable between where a foot should be, and the brain," Christiansen said. "I can almost feel my foot — my brain thinks it can feel where my foot is," he said.

The device is small and relatively unnoticeable. It only requires 30 minutes of use before your brain can recall the tone pattern on its own. Then you can discard the device for the rest of the day.

This solution shall not include mention to the use of drugs, chemicals or biologicals (including food); invasive devices; offensive, commercial or inherently dangerous content. This solution was not medically validated. Proceed with caution! If you have any doubts, please consult with a health professional.

About the author

Jon Christiansen, Richard Haselhurst and Steve Willens, from the USA, invented the Sensastep, an assistive walking device, for Jon, who has damaged most of the nerves below his left knee.